The present invention pertains to sampling and display systems and more particularly to waveform sampling and digitization for use in digital display devices or oscilloscopes.
Devices such as oscilloscopes permit the physical display or graphing of voltage, on a vertical axis, versus time, on a horizontal axis. From this visual display or graph, it may be determined how much of a given signal is direct current, how much is alternating current, how much is noise, what the frequency of the signal is and the manner in which the signal changes with time. These aspects of a signal can be displayed in analog form as part of one test using conventional oscilloscopes.
These conventional oscilloscopes accept an input signal. The scope scans the signal vertically and horizontally, that is to determine how the signal changes with voltage and with time. The oscilloscope is then triggered at a particular voltage or time to output an analog representation of the input signal on a display device such as a cathode ray tube. The electron beam of the cathode ray tube is deflected horizontally and vertically to graph or draw an image of the input signal as it changes in time and voltage.
Digital oscilloscopes are desirable since they can faithfully represent the input waveform with high resolution. However, digitally displaying a signal on an analog display device such as an oscilloscope is difficult.
One circuit for controlling the digital display of waveforms is shown in U.S. Pat. No. 4,654,584, issued on Mar. 31, 1987, to C. Gyles. A sampling system is shown in U.S. Pat. No. 4,536,760, issued on Aug. 20, 1985, to L. Navarro.
Accordingly, it is an object of the present invention to provide circuitry for depicting a digital representation of waveforms on an analog display device.